A conventional wireless local area network (WLAN for short) standard that is based on an orthogonal frequency division multiplexing (OFDM for short) technology includes gradually evolved versions such as 802.11a, 802.11n, and 802.11ac. A conventional WLAN system is still a half-duplex system in terms of wireless transmission. That is, any communications node including an access point (AP for short) and a station (Station, STA for short) cannot simultaneously send and receive data at any moment.
Currently, the IEEE 802.11 standardization organization has started to standardize a standard 802.11ax of a new-generation WLAN that is referred to as a high efficiency wireless local area network (High Efficiency WLAN, HEW for short). As a candidate technology, a full-duplex technology is used with uplink multi-user multiple input multiple output (Multi-user MIMO, MU-MIMO for short) and orthogonal frequency division multiple access (OFDMA for short) to reduce random contention and improve spectral efficiency of the WLAN system by means of multi-user transmission. The full-duplex technology allows a user in an uplink transmission direction and a user in a downlink transmission direction to simultaneously perform transmission on a same radio channel. In order to cancel self-interference from a transmitted signal to a received signal within a communications node, a self-interference cancellation operation needs to be performed on a receiver unit such as an antenna, an intermediate radio frequency, or a baseband. Therefore, the communications node needs to perform channel self-interference detection before performing communication.
Currently, there is no effective full-duplex communications solution in the WLAN system.